In the past, efforts have been made to increase the efficiency of cycles such as self-powered bicycles. These efforts have included improvements to the pedals that transmit force from the cyclist's foot to the axle that drives the crank arm. Such improved pedals coact with a cleat on the cyclist's shoe to efficiently receive downward force, upward force and forward and backward forces from the cleat. Another object of such pedals has been to provide ease of engagement of the cleat with the pedal, yet allow controlled release from the pedal. One type of pedal engagement/release is referred to as a "step-in, twist-out" pedal.
There are two design variations of the step-in, twist-out pedal. In pedals sold under the LOOK and KEEWIN trademarks, the cyclist's foot is held securely on the top surface of the pedal. Proponents of this design contend that when the cyclist's feet are correctly aligned on the pedals, the pedals deliver full force to the crank arm, but do not hurt the cyclist's legs.
The other basic philosophy of step-in twist-out pedals is that the cyclist's foot should be allowed to rotate freely on the top of the pedal. This is intended to allow the cyclist's leg to constantly twist or adjust its position around a vertical axis while pedalling, and avoid torsional stress on the knee joint in particular. These designs are sold under the trademarks AVENIR and TIME.
In the step-in, twist-out pedal designs that allow free rotation of the foot on the pedal, a pocket or recess is provided in the pedal and is larger than the corresponding projections of the cleat. In this manner, without actuating any detent that normally secures the cleat to the pedal, the cleat can rotate torsionally (in a generally horizontal plane around a generally vertical axis) to permit the cyclist's lower leg to freely rotate with the cyclist's upper leg. Such free or loose torsional movement of the cyclist's shoe cleat (and foot) relative to the pedal is commonly referred to as "floating."
Some of the step-in, twist-out pedals that provide a tight, yet releasable mating of the pedal with a shoe cleat, allow little if any torsional motion of the cleat on the top surface of the pedal before the release occurs or starts to occur. This is shown, for example, in U.S. Pat. No. 4,815,333, issued on Mar. 28, 1989, and invented by Applicant. In that SAMPSON pedal system, front and rear surfaces of the cleat are designed to mate with correspondingly shaped front and rear surfaces of the pedal. The mating surfaces tightly engage each other to transmit upward, downward and forward/backward forces from the shoe cleat to the pedal. These mating surfaces do not prevent movement of the cleat relative to the pedal around a vertical axis. However, such torsional movement is resisted by a spring-biased detent, such that the normal twisting force transmitted through the cyclist's knee to the cyclist's foot is resisted, which exerts torsional stress on the cyclist's knee. Thus, in the LOOK, KEEWIN and SAMPSON types of step-in, twist-out pedal designs, the cyclist's knee may be subject to torsional stress during pedaling.